First of all check out this great story by ebhg ( u/1730508/ ) ; Another's Favor ( s/9606092/1/Another-s-Favor ) (If you can't be bothered copying out that link go to google and type 'Merlin Mithian Fanfiction' and it should come up in the top 3.) It's amazing and one of my favourite stories and you definitely need to check it out! I recommend it wholeheartedly! Also, this story is set in the world of Another's Favorsomewhere between chapters 13 and 14. So it might help if you read that first.
However if you want to read this first or you simply don't want to read Another's Favor (though I strongly suggest you do!),I'll give you a summary of it here;
WARNING!*SPOILERS* for up to chapter 13 of Another's Favor and up to episode 4 Series 5 of Merlin.
Set immediately after 5x04 of Merlin, the knight's, Arthur, Gwen, Rodor, Mithian, Merlin, Gaius and Odin head back to Camelot to discuss what will happen next. Merlin and Mithian begin to grow close. Odin asks Rodor for Mithian's hand in marriage, seeing it as a way to gain power, which Rodor declines immediately.When Odin leaves Rodor realises he needs Mithian to marry to protect her from the likes of Odin. Seeing how much of a say Merlin has in the king's decisions and how close he and Mithian have grown, he offers Mithian's hand to the manservant, much to Merlin's shock. Merlin is then promoted to Arthur's First Advisor. Merlin and Arthur join the knights on a search for a missing patrol. Merlin's magic is revealed but he is accepted by all. Mordred is found but Arthur and Merlin (along with Gwaine and Mithian) must travel to the Cauldron of Arianrhod to cleanse him of a disease. Whilst there, a battle between Morgana and Merlin ensues and Morgana is defeated. However, during the battle Mithian is injured and seemingly dying. Merlin holds her, crying 'Not again, not again' but is reminded by Mithian of the waters healing powers and so Mithian is healed. The party then head back to Camelot.
Enjoy!
Merlin was tired. His whole body ached, a dark pain wracking his spine. He had, after all, just summoned the White Goddess twice, defeated a high priestess and watched as his beloved wife had taken a sword for him; pretty exhausting stuff, despite the way Arthur belittled his achievements. No ordinary man could do what he had just done and still be conscious be for the journey home.
Maybe then, it was due to his exhaustion that Merlin didn't spot the strange looks Arthur and Gwaine were throwing him, or the way the kept glancing at each other as if passing a secret message back and forth. Or maybe he was just tired of noticing.
Whatever the reason however, Mithian, sat with her back pressed to Merlin's chest as they rode along swiftly, was not so oblivious. Eventually, when she could herself back no longer, she turned to the pair and asked "Just what exactly is wrong with you two?!"
"Nothing" Gwaine and Arthur replied simultaneously, both glancing down with a sudden interest in their boots.
"Well it's obviously something or you wouldn't have looked so guilty" Mithian replied.
Arthurs head rose and he glanced nervously in the direction of Merlin and Mithian's horse. "It's just, well, you see-"
"Spit it out before you make an either bigger prat of yourself" Merlin joined the conversation, intrigued by what could be on the knight and king's minds.
"Well, back at the Cauldron, when Mithian was injured, and you were leaning over her, well, what did you mean?"
"What did I mean?" Confusion covered the warlock's face.
Arthur took a deep breath. "When you were holding her, you were sort of crying and you just kept saying 'Not again", well, what did you mean?"
"Oh" Realisation spread through Merlin's body. He felt an ache begin in his chest, slowly growing through every part of his body, swirling through his mind. Mithian too had now turned her gaze to Merlin and all present were looking at him questioningly.
Merlin started slowly, realising he had no choice but to tell this story. "Mithian… Mithian, no matter how much she may mean to me at present, was not the first woman I have loved."
Arthur looked confused. "What? You mean your mother?"
Merlin shook his head sadly. "No, well I love her too, but that's not what I mean." Merlin seemingly composed himself before continuing, a gleam of a tear thee only sign of the deep sadness within.
"Many years ago, before I had even met Mithian, just a few years into my life in Camelot, I met a girl. She- she too had magic, but she was hunted, she was being held in a bounty hunter.. I couldn't leave her, I couldn't, not when it could so easily have been me in that cage. And so, under the cover of darkness, I went back to her, and I freed her. I took her to the catacombs, I told her-" Merlin gulped down a wave of emotion, "I told her I'd keep her safe."
Merlin could hold it back no long, tears flooded his face and sobs wracked his body. Mithian turned to him and engulfed his body in hers, telling him without words she was here for him, and she loved him, although a part of her longed to know more about this girl. Gwaine and Arthur looked on, taken aback by the warlock's confession, unable to comprehend how they could never have seen the pain hidden inside of their friend.
Arthur was the first to speak. "What- what happened to her- the girl?"
Merlin lifted his head from Mithian's chest and looked to the grass before continuing.
"She was wonderful. She had long dark hair, soft and wavy, simple features, except for her eyes; her eyes were stunning, deep and brown and full off love and stories and sadness. I took her your food and one of Morgana's dresses; she looked just like a princess. I promised to look after her, that no one would hurt her. I was wrong. She was cursed. When she was younger she'd been attacked, in self-defence the man was killed, it wasn't her fault; she as scared. But the man's mother was a sorceress and when she found out what she had done, she cursed her to kill forevermore. And so each night she transformed, a bastet, and she would kill, she couldn't control it, she hated that part of herself; even the druids wouldn't accept her. I was going to run away with her, look after her, she could control herself in bastet form when I was there. We could have been happy. But she left. I went to get supplies and she left, scared that she'd lose control, hurt me, she said she didn't want to take me away from my life in Camelot. Only, before she could get out of the city, she transformed. And whilst in Bastet form she was mortally wounded. By the time I got there there was nothing I could do. So I carried her, to a lake with flowers and hills, just like she wanted and I held her in my arms as she went. I placed her on a boat. Burnt her. Held my own funeral. I thought I'd never love again, not until I met Mithian. And even then at first I was unsure, how could I truly contemplate loving another, it felt like I was betraying her. Then I realised it wasn't, she would have wanted me to be happy, but I still loved her. When saw Mithian today, with that, that wound, I couldn't bear it, for the same thing to happen. I couldn't."
Merlin stopped, whether because there was nothing left to say or simply because he couldn't continue, Mithian didn't know but she pulled him back towards him and whispered softly into his hair.
"It's okay Merlin, I'm here, I'm here."
Arthur face twisted at the thought of his friend going through it all alone. He couldn't understand, why hadn't he told him, and more importantly, why hadn't he realised? Surely if something had upset Arthur then Merlin would have notice in an instant, in fact he usually did notice in an instant.
"Merlin, I'm sorry, I should have known, I should have seen."
Gwaine seemed to agree a little too strongly with his sentiments. "Yes, Princess, you should have seen, you should have known, you should have noticed that your best friend was grieving on his own!." His voice had risen to a shout by the end but Arthur didn't deny it or attempt to defend himself, instead he simply looked Gwaine in the eye and acknowledged his guilt.
"I'm sorry."
With that he rode and Mithian pushed hers and Merlin's horse to follow, Gwaine moments behind. Silence enveloped them, bringing with it a cold breeze, allowing each person to become lost in their own thoughts.
They continued like this for a few more minutes before, the King turned his head back to Merlin, one last question on his lips. However, the words had not even left his tongue when they were answered.
"Freya, her name was Freya."